1. Field of the Invention
This invention relates generally to height adjustable false bottoms for pools, and more particularly to an improved apparatus for effectively and efficiently raising and lowering the false bottom.
2. Discussion of the Related Art
Such height adjustable false bottoms are used in particular in swimming pools or multi-purpose pools, where the depth of the pool is to be adjusted to different requirements by means of the height adjustable false bottom. The height adjustment is often made while the pool is filled with water.
A height adjustable false bottom of the general type in question is disclosed in German patent 2,261,404. That German patent document is incorporated herein by reference. That German reference describes one possibility of a making an adjustment by means of supporting legs of invariable length, attached undisplaceably to the false bottom at their upper ends. The lower ends are moved by a suitable drive, especially a spindle drive, thereby achieving an adjustment of the height of the false bottom. This system functions generally satisfactorily in operation.
One disadvantage of the apparatus disclosed in that reference, however, is that a relatively long period of time is required to achieve the total lift. Specifically, a period of about 12 minutes is required with these known systems to travel a height of about two meters. Furthermore, this lifting operation does not always proceed uniformly. Depending on the position of the supporting legs, the false bottom is raised either rapidly or slowly. A disproportionately long period of time is required, especially for lifting the false bottom into the topmost position.
Another disadvantage of the prior apparatus is that the minimum structural height of this height adjusting device is about 700 mm. This means that excavation for the pool must be more than 0.7 m deeper in the area of the height adjusting device, with appropriate waterproof lining accordingly.
In addition, there are also known hydraulic systems consisting essentially of a vertically arranged hydraulically operated jack supporting the false bottom. These systems can handle much larger forces, but they are expensive to manufacture and also require high maintenance. One serious disadvantage of these hydraulic systems is that the gaskets used are not completely oil-tight. Thus they necessarily cause contamination of the water. This contamination is substantial. Under normal operation, 30 liters of fresh water are added to a pool per swimmer in a certain period of time. This value increases to 300 liters when these hydraulic lift systems are used.